Re: 12 volt power source?

Ray Haddad wrote:

On Wed, 26 Dec 2007 14:59:27 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Ray Haddad wrote:

On Wed, 26 Dec 2007 10:13:33 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Ray Haddad wrote:

On Wed, 26 Dec 2007 07:30:19 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Ray Haddad wrote:

On Mon, 24 Dec 2007 09:36:14 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Ray Haddad wrote:

On Mon, 24 Dec 2007 08:34:58 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Here's a laboratory power supply from Jaycar Electronics:
<http://www1.jaycar.com.au/productView.asp?ID=MP3078&CATID=&keywords=Bench+power+supply&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=>

Here's a laboratory power supply from *** Smith Electronics:
<http://dseau.resultspage.com/search.php?sessionid=476eb5e50123fe3a273fc0a87f9c0718&w=Power+supply+13.8&site=&submit.x=11&submit.y=8>

Sorry the links are so long but that takes you to the specific product.

I've been involved with fitting ship, boat and truck radio/depth finding
etc gear (AWA NZ, a division of RCA USA) All our gear was rated at 13.8
volts because that's the operating voltage found on batteries in circuit
in those situations.

That's because they run from a generator or an alternator and not a
12 volt battery which is never, ever going to be at 13.8 volts.

LOL.

The battery is in circuit between the generator/alternator and the load,
it's an integral part of the voltage regulation circuit.
If the alternator and the load are at 13.8 volts then the battery _must_
be at ...?

No, Greg. The entire CIRCUIT is at 13.8 volts.

Exactly Ray - geeze, it really takes a _long_ time for you to not
understand the completely obvious!

Baloney. You've been spewing from the mountaintops that a 12 volt
battery will measure 13.8 volts and that's simply wrong. Don't try
to weasel out of it now. Everyone here has been trying to convince
you that the CHARGING circuit is 13.8 volts and now you pretend you
knew it all along.

A 12 volt battery will not ever measure 13.8 volts as you stated.

That battery company I cited is going to be very disappointed!

They're on the same page as me, Greg. Why would you believe
otherwise?

Not the battery. When
you turn off the motor, the battery drops to 12 volts just like
always.

Why do you keep stating that which is only correct when the battery is
at 12 volts?

Because a 12 volt battery will never, ever measure 13.8 volts. Ever.

In that case the car electric connected to said battery will never
measure 13.8 volts. Ever.

Exactly. Not without external potential added. A battery circuit,
including the battery, can be driven to a higher voltage but that
process is known as charging. When used as a source of power, a
battery will never be at 13.8 volts. It's a physics thing.

Awww Ray, if the electrical circuitry of the car is at 13.8 volts then
the battery is at 13.8 volts - it's a physics thing.

No, it's not. When you remove the 13.8 volt source, which is NOT the
battery, the battery remains at 12 volts. Period.

We will just have to agree to differ on that point - all my multimeters
agree with me.


The information that voltages above 13.8 volts will cause gassing is
sort of wasted really.

That's what the float limit is all about. Gassing causes the
electrolyte's hydrogen to leave the battery. It's a serious issue.
If you charge at too high a voltage, the electrolyte outgasses and
you get spidering between the cells which can cause cell failure.
Water vapor also escapes during gassing which lowers the levels.

I do hope you mean _to_ too high a level? If you charge a battery it has
to rise through every voltage point from start to ...

No, Greg. If you were to say use 20 volts to charge, that would be
too high a level.

Basic Ohms law here:
Input voltage (minus voltage sources in circuit) / resistance = current
flow.
13.8v+ / resistance = excessive current.

There's no way to charge a 12 volt battery to any
old voltage you choose. Even 13.8 volts is impossible.

That's the voltage my cite claims is possible. Even your cite said 13.2
volts+.

Thus, when
the charge voltage is removed, the battery is at 12 volts.

That doesn't agree with reality.

If the charge level is less than 12 volts you won't find 12 volts across
the terminals.


No more
than that or just barely above it.

Just barely above it?? 12.5? 13? 13.2?

Certainly that battery will never
be charged to 20 volts or even 13.8 volts.

13.8 volts is the (safe) limit.

You're grasping at straws
now, Greg.

I'm still holding the same straws I started with.



Gel
batteries don't suffer that same fate but an overcharge voltage on
them can cause swelling and cell failure from heat.

It's best not to overcharge those either - however, they still have to
be charged from their starting point through every voltage point to
overcharge.

Lead-acid batteries are nearly impossible to overcharge but if you
apply to high a float potential you will get gassing or outgassing.

That has to do with resistance/current flow.


You really don't understand batteries. Just leave it at
that. Otherwise you'll keep on making a fool of yourself.

This one bears repeating. You simply don't understand batteries,
Greg.

Fair point - care to design my current electric car design for me?

No thanks, mate. I'm converting one now. A Dihatsu Mira-J. I'm so
pleased about how clean the car has become since the engine is gone.
I've got 3 years invested in it and don't expect to finish for at
least another 3. Batteries (huge power sources) are getting cheaper
and different every day.

I've just put aside the idea of building a car from scratch and am
looking for something like the Daihatsu Mira.
There's not enough years left!

I decided to make it rear wheel drive with the entire front
compartment reserved for batteries. I'm experimenting with the fuel
cells. Two motors on the rear and all the power and most of the mass
up front. Since the mass is all between the axles front to back,
that will make it a very stable vehicle. Small, but stable.

I was designing a minimal two in-line seat 4 wheel vehicle to minimise
wind and rolling resistance. Building and certifying such a vehicle
could be a long process.
I now have to start over with an existing vehicle and extrapolate
everything I've done so far.


Have you looked at the commercially available fuel cells? Brilliant!
http://www.batterybook.com/default.asp

Look in the middle column, third one down. The best part? They're
literally a few miles away from me.

Now, Greg, I'm offering you a Boxing Day olive branch. Can we end
this seemingly endless debate and get back to trains?

What did you think of the fuel cells?

I still have to get to that, rellies here until an hour ago. However it
has to be something I can obtain here, at a workable cost.
.